Yeah, I went back and re-read the thread and just saw that. I've read of people using blenders to mix the DME so you should be fine.
ETA: I was looking for this video earlier but got distracted. He tries four methods to combine the DME with water. The fourth is via blender (starts at 2:20), which in the description of the video was described as "surprisingly effective".

My first time stationed in Germany was 1995-1996. I was in the dorms on base. We had Coke vending machines in the common room on each floor. The bottom selection on each one was always a beer. Sadly, it was some form of Budweiser: Bud, Bud Light, Bud Dry, or Bud Ice.

I'm brewing the Suava Java later today. It uses the American Lager, LME, 1 lb grains, a hop addition, and coffee. If that doesn't elevate it from "f'in close to water beer" I don't know what will.
Edited: make that 3/4 lb grains.

Three weeks is optimum to ensure fermentation is complete. Four weeks shouldn't hurt the beer. But from what I've read you don't want to go beyond that as off-flavors can be produced by the beer sitting on the trub that long.

They'll both achieve the same result. With "regular" sugar you have more control over the carbonation. It's easy to fine tune to your preferred carbonation level. Some folks batch prime so they don't have to deal with adding sugar to every bottle (look about half-way through this post for a tutorial on batch priming). I just use Domino's Dots. One cube = 1/2 tsp. I use one cube for 12 oz bottles, two for 16 oz or 500 ml bottles.

What size bottle was it and how much priming sugar did you use?
The consensus is that the MRB recommendation for priming sugar results in an over-carbonated beer. Here's a thread that discusses better recommendations. I keep things simple:
12 oz. bottle = 1/2 tsp (one Domino's Dot)16-17 oz. bottle = 1 tsp (two Domino's Dots)
I vary it slightly based on style of beer I'm making, but for the most part that's my method.
As for head retention, that's not uncommon with extract brews. Once you make the step up to partial-mash brews you'll notice that the addition of grains helps with the head. I steep some carapils with every recipe I make just to help with body and head retention.
As a side note, head retention isn't an indicator of the quality of a brew. I was at a brew pub last weekend and had these two beers. Neither of them had much head to speak of but both were quite tasty.

A side note on the A.M. beer thing-
My wife and I were stationed in Germany for almost seven years. Beer is just part of the culture over there so you get used to seeing folks drinking it while on their lunch break. But what I always got a kick out of was when we'd be flying somewhere. We'd get to the airport at 6:00 a.m. and there were already Germans drinking beers while waiting for their flights. Apparently the vacation started as soon as they got through security.